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Case of the Week #137

Clinical
History

A 72 year old man had a
radical prostatectomy for prostatic adenocarcinoma.

Prostatic melanosis is the finding
of melanin within prostatic stromal melanocytes and glandular cells. The
stromal melanocytes are believed to transfer melanin to the epithelial cells (Am J Clin Pathol
1988;90:530). Prostatic melanosis may be an isolated finding, associated with blue
nevus (Eur Urol 1992;22:339) or associated with other prostatic
pathology such as adenocarcinoma, as in this case.

The differential diagnosis includes lipofuscin
pigment and blue nevus. Although lipofuscin is characteristic of ejaculatory
ducts and seminal vesicles, it is also found in prostatic epithelium (Am J Surg Pathol
1994;18:446, Mod
Pathol 1996;9:791). It is composed of golden yellow-brown to gray-grown granules (lipofuscin in
hepatocytes). It stains with PAS-diastase, Congo Red, Luxol fast blue, Oil red O and Ziehl-Neelsen. Both lipofuscin and melanin stain with
Fontana-Masson stain, but lipofuscin is S100 negative.